1. Field of the Invention
This invention relates to wood deck construction of the cantilevered, circular, or freeform type.
2. Description of the Prior Art
The use of cantilever type wood deck platform construction has existed for many years. Typically this construction utilizes a substructure including inground footings that support the main beams upon which a joist structure is framed. Joists are placed on top of the main beams at intervals, which are usually sixteen inches on center. The joists cantilever past exterior beams commonly a distance of twenty-four inches, which results in a less visible deck substructure. The prior art systems are primarily utilized for large or freestanding deck platforms that by design can not be attached to an adjacent structure by ledger beams do not or can not contain a perimeter flush beam header, or perimeter post support system; or require projection over and beyond a fixed object such as a wall or bulkhead.
The use of decks to provide outside areas for asthetic considerations, or for entertainment has greatly expanded in recent years. The desire to provide a deck construction that can accomplish the desired asthetic effect while still maintaining structural integrity and keeping the cost low has proven difficult.
In cantilevered framing, the recommended framing configuration includes a perimeter structural member known as a "rim", "band", or "ribbon" joist. When perpendicular to joists the member serves, as a "header" or "trimmer" that ties the individual joists together, and does not significantly contribute to deck surface support. When the member is parallel to internal joists it acts as the exterior structural joist member, which is responsible to carry the deck surface weight on the exterior span. The rim joist may be positioned at an angle to the joists without compromise of strength (when properly supported by beam sub-structure) and with little added carpentry skill. A fascia may be added to the perimeter joist to provide a decorative facade, or a separate structure attached to and utilizing the perimeter joist may function as skirting to elimiate sub-structure visibility.
In flush beam deck platform framing, the perimeter member or "header" is the structural beam from which all joists are supported or "hung". The joists are set between beams and normally rest on an attached "ledger" with the flush beam supported by perimeter posts.
While both systems serve well for their intended function in the construction of wood platform decks of rectangular or angled perimeter shape, a rigid wood exterior structural member on the flush beam normally precludes its use for circular or freeform shapes that utilize flexible or bent wood members. At present three variations of the construction system utilizing cantilevered joists are available, when a circular or freeform shape is desired.
The first method is based on bending the perimeter structural member to the desired shape, and then securing it to the joists that have been pre-cut to perimeter shape. As the perimeter wood member size increases or the radius of the bend decreases, "kerfing" of the member is required. "Kerfing " which involves saw blade cutting of a wood member at prescribed intervals to a partial depth to remove stock and enable wood to become more flexible, of any wood member reduces its structural strength, integrity, and fastening ability. It is very difficult to achieve a true arc or radius, when small dimensions or reverse curves are required, by bending wood intended for strutural members, even when kerfed. Fastening and in place retention of the actual member as well as the fastening of deck surfaces and fascia to this member present equally difficult challenges. Costs in labor and material are unpredictable at best.
The second method utilizes lamination, etiher horizontal or vertical, of layers of wood members to achieve the perimeter shape of the deck. Both dimensional requirements and fastening problems exist in this method and the "on site" or "in shop" milling, gluing-up and clamping of perimeter members results in time inefficiency, and extremely high costs of material and labor-supervision. This method is used infrequently for sub-structures.
The third and most prevalent method of creating circular or freeform deck shapes as viewed from the deck surface is achieved with the sub-structure constructed in a segmented circle. Short lengths of perimeter joists are set on angles following the exterior radius or arc of the deck surface. This method does not achieve a sub-structure that is aesthetically mated to the circular or freeform surface, and requires the use of extended, unsupported surface overhang, resulting in deck edge instability, and does not achieve a true circular or freeform deck.
The deck construction of the invention provides structures built to tru arc configuration, that have high structural integrity, and are of relative low cost, simple construction.